This invention relates to waveguide switches and, more particularly, to a pair of waveguides with a common wall in which are located a pair of coupling windows and rectractable shutter elements or gates for selectively coupling differing amounts of power among plural output terminals of the switch.
Switches for selectively coupling electromagnetic energy between waveguides are employed in a variety of situations. One situation of particular interest is in the construction of an antenna composed of an array of radiating elements. As is well known, both the relative phases and the relative amplitudes among microwave signals applied to the respective elements determines the direction and the shape of a resultant beam of radiation. While the number of radiating elements and the spacings therebetween set limitations on the shape of a beam, a substantial amount of beam shaping can be accomplished by varying the amplitude of signal applied to each of the radiating elements.
A case of particular interest involves the stepwise, or digital, switching of microwave power to selected ones of the radiating elements. In a large array, effective beam shaping can be accomplished by the simple expedient of applying full power, half power or zero power to selected ones of the radiating elements.
One example of the use of such an antenna system, incorporating both the antenna array and the switches, is the antenna system carried by a satellite circumnavigating the earth. As the satellite passes over a specific country, such as the United States, it is desirable to continuously reform the radiating beam of the antenna so as to illuminate certain areas of the country. For example, it may be desirable to illuminate the northeast and southeast portions, and subsequently the northwest and central portions of the country. The beam can be adaptively reconfigured as the satellite passes over the country by the use of electronically activated switches which switch the electromagnetic power selectively among the various antenna elements to provide a desired shape to the beam.
A problem arises in that one form of switch which has been proposed for use in such a satellite antenna system is limited to two possible switch configurations, namely, coupling input power to either of two output terminals of the switch. Thus, a transmitter or receiver connected to an input terminal of the switch can be coupled to either of two branches of a microwave network or to either of two radiating elements of the antenna. However, the switch is disadvantageous that an alternative distribution of power, particularly the coupling of one-half of the power from one output terminal and one-half of the power by the other output terminal cannot be accomplished. This provides an undesirable limitation upon the capability and facility for continuous reconfiguration of the beam of radiation.